This invention relates to apparatus for use with a conventional bore spud for mounting and positioning a conventional collimator with respect to a sighting device or scope on a firearm for bore sighting the firearm and more particularly to such apparatus which provides for adjustably positioning the collimator to an unlimited number of linear and angular positions with respect to the bore spud for enabling the collimator to be precisely aligned with the sighting device or scope.
A scope is an optical sighting device which is mounted on a rifle, shotgun or handgun. All scopes serve to enhance the shooter's ability to acquire a given target. Some scopes do this by magnification, which provides great accuracy at long distances. Others have little or no magnification but rather provide faster acquisition of a given target. All scopes must have a reticle or point of aim, the means by which to adjust the point of aim, a casing in which to house the reticle, and the means or ability with which to mount the scope onto a firearm.
A reticle, which is a center point in a scope, often appear as a cross hair, or in some scopes as a colored dot, often red. The cross hair or dot is placed on the intended target by the shooter looking through, from the rear of the scope. When a scope is first installed onto a firearm, be it a rifle, pistol or shotgun, the scope must first be "sighted in" before it will serve to accurately aim the firearm. A scope is typically "sighted in", by way of mechanical adjustments, for elevation and windage. The process of sighting in can be performed at a target range by shooting at a target and adjusting the scope's reticle to the point of impact. However, this process can be both time consuming and costly to the shooter.
In order to expedite this "sighting in" process, others have developed a means and a device to accurately adjust a scope with respect to the barrel of the firearm onto which the scope is mounted. This process is commonly referred to as "bore sighting", and the device, developed by others, by which this is accomplished is commonly referred to as a collimator.
A collimator is attached to the front of the firearm by way of a "bore spud". A bore spud is a rod of metal approximately three and one-half inches in length which either fits the inner diameter of the firearm's barrel or mechanically expands to match the barrel's inner diameter. The bore spud is placed inside the muzzle of the firearm with approximately one inch protruding. The collimator is then fastened onto the bore spud, placing it directly above the bore of the firearm.
A collimator has an opening on one end which faces the rear of the firearm. Inside the collimator is a very small grid screen with cross hair lines running both vertically and horizontally through the center. With the collimator installed, the shooter sights through the scope and into the collimator. The shooter can now make windage and elevation adjustments to the scope and align the cross hair or dot of the scope with that of the collimator's cross hair. This process, when performed correctly, can be very close to the firearm's "true" point of impact on a real target at roughly one hundred yards.
When a firearm is brought to a gun shop for service it may already be equipped with a scope or optical sighting device. In order to properly service the firearm, the scope is removed.
Before removing the scope, the technician will note where the scope's reticle is adjusted in relation to the firearm's bore. This is done by first installing a collimator. The technician then sights through the scope and into the collimator, viewing the point at which the scope's reticle vertically and horizontally intersects on the collimator's grid screen. This enables the technician to write down precisely where the fire-arm's owner has adjusted the scope. The technician can now remove the scope along with the collimator assembly and proceed with the repair. When service to the firearm is complete, the technician installs the scope along with the collimator assembly and adjusts the scope's reticle to the previously noted point on the collimator.
Various types of collimator mounting devices are known. Examples are described in U.S. Pat. No. 5,222,302 and in UK patent application GB2194621A. Although such devices have served the purpose, they have not proved entirely satisfactory because they allow for only a limited number of discrete positions for the collimator with respect to the firearm sighting device or scope. These devices often allow for positioning of the collimator only at a too low or too high location for proper alignment with the firearm scope, and in some situations the collimator cannot be properly viewed through the scope for accurately bore sighting the firearm. Some collimator mounting devices will partially obstruct the view of the collimator through the scope, thus compromising the accuracy of alignment of the collimator with the scope. Some collimator mounting devices also do not permit for angular positioning of the collimator with respect to the firearm bore to permit proper alignment of the collimator with the firearm scope when the scope is offset and not positioned directly above the firearm bore.
It is, therefore, an object of the present invention to provide apparatus for use with a bore spud for mounting and positioning a collimator with respect to a sighting device or scope on a firearm for bore sighting the firearm.
Another object is to provide such apparatus which enables the collimator to be adjusted to an unlimited number of linear and angular positions with respect to the firearm bore.
A further object of the invention is the provision of such apparatus which will enable precise alignment of a collimator with a firearm sighting device or scope during the bore sighting process.
A further object of the invention is the provision of such apparatus which allows positioning of a collimator above or below the center of the firearm bore.
Another object of the invention is to provide such apparatus which enables positioning of a collimator at an angularly displaced location to the left or to the right of the center line of the firearm bore to position the collimator in precise alignment with an offset firearm sighting device or scope.
Yet another object of the present invention is the provision of such apparatus which enables positioning of a collimator at an angularly displaced location to the left or to the right of the center line of the firearm bore while maintaining the grid screen of the collimator in vertical and horizontal alignment with the reticle of the offset firearm scope or sighting device.
A still further object is to provide such apparatus which can be used with bore spuds of various sizes and diameters.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages are realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.